Today I used a cheap external active GPS antenna with a thin 5 m cable (see attached DS), but I had to solder SMA connector instead of unknown to me. The current consumption of the antenna 11мА @ 3V. About 2 minutes after a cold start, the status LED starts blinking 0.5 Hz and 1PPS signal appears at the Clock output connector. So, now we can to start work with the self-tuning of the TCXO.
Anyway, how realistic in the near time to implement an simple command translator through the FTDI - FPGA for the SPI to each LMS to get at least the signals of their synthesizers (also to UART for GPS, to SPI for DAC of TCXO and etc. :). It can be a simple protocol with virtual control registers addressing and read/write or a few separate firmwares for each goal. With such a tool at any time we will be able to check UmTRX operation with some simple signals and an spectrum analyzer. Also it will be very helpful for the understanding of how to work with LMS control registers, which is poorly described in the documentation. Have any thoughts or suggestions on this?
Best regards, Andrey Sviyazov.
2012/1/20 Andrey Sviyazov andreysviyaz@gmail.com:
Today I used a cheap external active GPS antenna with a thin 5 m cable (see attached DS), but I had to solder SMA connector instead of unknown to me. The current consumption of the antenna 11мА @ 3V. About 2 minutes after a cold start, the status LED starts blinking 0.5 Hz and 1PPS signal appears at the Clock output connector. So, now we can to start work with the self-tuning of the TCXO.
Yes, this is definitely a thing to do. Andrey, could you take on calibrating PID regulator if someone adds it to the code?
Anyway, how realistic in the near time to implement an simple command translator through the FTDI - FPGA for the SPI to each LMS to get at least the signals of their synthesizers (also to UART for GPS, to SPI for DAC of TCXO and etc. :). It can be a simple protocol with virtual control registers addressing and read/write or a few separate firmwares for each goal. With such a tool at any time we will be able to check UmTRX operation with some simple signals and an spectrum analyzer. Also it will be very helpful for the understanding of how to work with LMS control registers, which is poorly described in the documentation. Have any thoughts or suggestions on this?
We must get this working asap to be in time for MWC with testing.
Andrew Karpenkov should be looking into connecting with LMS right now. Andrew, could you please report your progress?
Regarding I2C/SPI - there is already some way to communicate with those buses from a host. I don't recall exact API, though.
For UART they have created a nice way, so called UDP/UART. As I understand it they just stream UART data over UDP in both directions. The code was added after we branched off fairwaves/umtrx. We should rebase our code to some point after Sept 28 to get this functionality. Andrew Karpenkov - could you please do this asap?
Here are some pointers. Commit with UART/UDP feature: https://github.com/EttusResearch/UHD-Mirror/commit/25494489bf8b7c60875ea355d...
How to use it: http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2011-December/00... http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2011-December/00...
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Alexander Chemeris -
Andrey Sviyazov